Area Forecast Discussion
Issued by NWS Paducah, KY

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FXUS63 KPAH 211728 AAA
AFDPAH

Area Forecast Discussion...UPDATED
National Weather Service Paducah KY
1228 PM CDT SUN AUG 21 2016

.UPDATE...
Issued at 1228 PM CDT Sun Aug 21 2016

Updated the AVIATION discussion for the 18Z TAF issuance.

&&

.SHORT TERM...(Today through Tuesday)
Issued at 145 AM CDT Sun Aug 21 2016

At this writing, the surface cold front has not quite made its
passage across the entire FA...still lingering across the
Pennyrile of western Ky, where an associated band of showers was
seen parading across the region with rainfall rates up to an inch
and a half an hour in the still soupy, lower 70s TD`s air residing
there. Further northward and westward, behind the front, already
mid to upper 60s dew points were encroaching, with clearing skies
not far behind.

At their present rate, we project the showers across our
southeastern-most counties to be departed by 12Z, although an
isolated linger beyond is not out of the question. Thereafter, we
should see the drier dew points work in, as the center of surface
high pressure expands from KS-OK into/across MO. Clearing skies
with plentiful sunshine will result, and upstream trajectories
suggest dew points down into the 50s FA-wide by early Monday
morning.

As the High shifts eastward to the middle Ohio river valley
by Tuesday, return flow around the High will see dew points climb
back into the 60s, with upper 60s/near 70 possible in the SEMO
Ozarks by late Tuesday afternoon. And while there is no strong
surface reflected boundary, backing flow aloft will allow modest
H5 Positive Vorticity Advection to present a short wave of energy
to the same SEMO Ozarks region, where daytime heating will have
produced 0-1KM MUCapes on the order of 500-1000 J/KG. This could
be enough of a combo of moisture/instability/lift to touch off at
least a few showers/storms, so we`ve included a small chance
there in our 4-6 western most SEMO Ozark counties to account.

.LONG TERM...(Tuesday night through Saturday)
Issued at 145 AM CDT Sun Aug 21 2016

All models in general agreement with the upper air and surface
pattern at the start of the period. At the upper levels, a ridge is
over the southeast U.S. and extends northward to the Great Lakes. An
upper level low is along the Canadian border with North Dakota. At
the surface, southerly flow is just starting to begin.

By 12z Wednesday moisture begins to return in earnest just ahead of
a shortwave passing mainly to our north. Model soundings suggest
that moisture will mix down during the day which will create a
noticeable increase in the dew point back into the mid 70s. GFS and
GEFS are slower on the returning moisture compared to the 12z ECMWF.

The upper level low along the Canadian border is forecast to move
east and open up. An 80-90 kt jet is forecast to develop ahead of
the low. This should help a weak front to reach the Ohio River by
00z Friday and should move south of the area by the end of Friday.

Only isolated showers and storms expected during the day on
Wednesday with slightly greater coverage Wednesday Night through
Thursday Night ahead of the front. PWs are forecast to remain below
2 inches, so localized heavy rain a possibility, but widespread
heavy rain is not expected at this time.

&&

.AVIATION...
Issued at 1228 PM CDT Sun Aug 21 2016

Aside from possible IFR/MVFR vsbys between 09-12Z, VFR conditions
should prevail at all sites through the period. Northwest winds
AOB 10 knots early will become light and variable/calm after
00-01Z, then pick back up out of the southeast AOB 5 knots after
15Z.

&&

.PAH Watches/Warnings/Advisories...
IL...None.
MO...None.
IN...None.
KY...None.
&&

$$

SHORT TERM...DH
LONG TERM...PS
AVIATION...JP



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